Interface SortedMap<K,V>

Type Parameters:: K - the type of keys maintained by this map; V - the type of mapped values

All Superinterfaces:: Map<K,V>, SequencedMap<K,V>

All Known Subinterfaces:: ConcurrentNavigableMap<K,V>, NavigableMap<K,V>

All Known Implementing Classes:: ConcurrentSkipListMap, TreeMap

public interface SortedMap<K,V> extends SequencedMap<K,V>

A Map that further provides a total ordering on its keys. The map is ordered according to the natural ordering of its keys, or by a Comparator typically provided at sorted map creation time. This order is reflected when iterating over the sorted map's collection views (returned by the entrySet, keySet and values methods). Several additional operations are provided to take advantage of the ordering. (This interface is the map analogue of SortedSet.)

All keys inserted into a sorted map must implement the Comparable interface (or be accepted by the specified comparator). Furthermore, all such keys must be mutually comparable: k1.compareTo(k2) (or comparator.compare(k1, k2)) must not throw a ClassCastException for any keys k1 and k2 in the sorted map. Attempts to violate this restriction will cause the offending method or constructor invocation to throw a ClassCastException.

Note that the ordering maintained by a sorted map (whether or not an explicit comparator is provided) must be consistent with equals if the sorted map is to correctly implement the Map interface. (See the Comparable interface or Comparator interface for a precise definition of consistent with equals.) This is so because the Map interface is defined in terms of the equals operation, but a sorted map performs all key comparisons using its compareTo (or compare) method, so two keys that are deemed equal by this method are, from the standpoint of the sorted map, equal. The behavior of a tree map is well-defined even if its ordering is inconsistent with equals; it just fails to obey the general contract of the Map interface.

All general-purpose sorted map implementation classes should provide four "standard" constructors. It is not possible to enforce this recommendation though as required constructors cannot be specified by interfaces. The expected "standard" constructors for all sorted map implementations are:

A void (no arguments) constructor, which creates an empty sorted map sorted according to the natural ordering of its keys.
A constructor with a single argument of type Comparator, which creates an empty sorted map sorted according to the specified comparator.
A constructor with a single argument of type Map, which creates a new map with the same key-value mappings as its argument, sorted according to the keys' natural ordering.
A constructor with a single argument of type SortedMap, which creates a new sorted map with the same key-value mappings and the same ordering as the input sorted map.

Note: several methods return submaps with restricted key ranges. Such ranges are half-open, that is, they include their low endpoint but not their high endpoint (where applicable). If you need a closed range (which includes both endpoints), and the key type allows for calculation of the successor of a given key, merely request the subrange from lowEndpoint to successor(highEndpoint). For example, suppose that m is a map whose keys are strings. The following idiom obtains a view containing all of the key-value mappings in m whose keys are between low and high, inclusive:

  SortedMap<String, V> sub = m.subMap(low, high+"\0");

A similar technique can be used to generate an open range (which contains neither endpoint). The following idiom obtains a view containing all of the key-value mappings in m whose keys are between low and high, exclusive:

  SortedMap<String, V> sub = m.subMap(low+"\0", high);

This interface is a member of the Java Collections Framework.

Since:

1.2

See Also:

Nested Class Summary

Nested classes/interfaces declared in interface Map

Map.Entry<K,V>

Modifier and Type	Interface	Description
`static interface`	`Map.Entry<K,V>`	A map entry (key-value pair).

Method Summary

Modifier and Type	Method	Description
`Comparator<? super K>`	`comparator()`	Returns the comparator used to order the keys in this map, or `null` if this map uses the natural ordering of its keys.
`Set<Map.Entry<K,V>>`	`entrySet()`	Returns a `Set` view of the mappings contained in this map.
`K`	`firstKey()`	Returns the first (lowest) key currently in this map.
`SortedMap<K,V>`	`headMap(K toKey)`	Returns a view of the portion of this map whose keys are strictly less than `toKey`.
`Set<K>`	`keySet()`	Returns a `Set` view of the keys contained in this map.
`K`	`lastKey()`	Returns the last (highest) key currently in this map.
`default V`	`putFirst(K k, V v)`	Throws `UnsupportedOperationException`.
`default V`	`putLast(K k, V v)`	Throws `UnsupportedOperationException`.
`default SortedMap<K,V>`	`reversed()`	Returns a reverse-ordered view of this map.
`SortedMap<K,V>`	`subMap(K fromKey, K toKey)`	Returns a view of the portion of this map whose keys range from `fromKey`, inclusive, to `toKey`, exclusive.
`SortedMap<K,V>`	`tailMap(K fromKey)`	Returns a view of the portion of this map whose keys are greater than or equal to `fromKey`.
`Collection<V>`	`values()`	Returns a `Collection` view of the values contained in this map.

Methods declared in interface Map

clear, compute, computeIfAbsent, computeIfPresent, containsKey, containsValue, equals, forEach, get, getOrDefault, hashCode, isEmpty, merge, put, putAll, putIfAbsent, remove, remove, replace, replace, replaceAll, size

Modifier and Type	Method	Description
`void`	`clear()`	Removes all of the mappings from this map (optional operation).
`default V`	`compute(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction)`	Attempts to compute a mapping for the specified key and its current mapped value, or `null` if there is no current mapping (optional operation).
`default V`	`computeIfAbsent(K key, Function<? super K, ? extends V> mappingFunction)`	If the specified key is not already associated with a value (or is mapped to `null`), attempts to compute its value using the given mapping function and enters it into this map unless `null` (optional operation).
`default V`	`computeIfPresent(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction)`	If the value for the specified key is present and non-null, attempts to compute a new mapping given the key and its current mapped value (optional operation).
`boolean`	`containsKey(Object key)`	Returns `true` if this map contains a mapping for the specified key.
`boolean`	`containsValue(Object value)`	Returns `true` if this map maps one or more keys to the specified value.
`boolean`	`equals(Object o)`	Compares the specified object with this map for equality.
`default void`	`forEach(BiConsumer<? super K, ? super V> action)`	Performs the given action for each entry in this map until all entries have been processed or the action throws an exception.
`V`	`get(Object key)`	Returns the value to which the specified key is mapped, or `null` if this map contains no mapping for the key.
`default V`	`getOrDefault(Object key, V defaultValue)`	Returns the value to which the specified key is mapped, or `defaultValue` if this map contains no mapping for the key.
`int`	`hashCode()`	Returns the hash code value for this map.
`boolean`	`isEmpty()`	Returns `true` if this map contains no key-value mappings.
`default V`	`merge(K key, V value, BiFunction<? super V, ? super V, ? extends V> remappingFunction)`	If the specified key is not already associated with a value or is associated with null, associates it with the given non-null value (optional operation).
`V`	`put(K key, V value)`	Associates the specified value with the specified key in this map (optional operation).
`void`	`putAll(Map<? extends K, ? extends V> m)`	Copies all of the mappings from the specified map to this map (optional operation).
`default V`	`putIfAbsent(K key, V value)`	If the specified key is not already associated with a value (or is mapped to `null`) associates it with the given value and returns `null`, else returns the current value (optional operation).
`V`	`remove(Object key)`	Removes the mapping for a key from this map if it is present (optional operation).
`default boolean`	`remove(Object key, Object value)`	Removes the entry for the specified key only if it is currently mapped to the specified value (optional operation).
`default V`	`replace(K key, V value)`	Replaces the entry for the specified key only if it is currently mapped to some value (optional operation).
`default boolean`	`replace(K key, V oldValue, V newValue)`	Replaces the entry for the specified key only if currently mapped to the specified value (optional operation).
`default void`	`replaceAll(BiFunction<? super K, ? super V, ? extends V> function)`	Replaces each entry's value with the result of invoking the given function on that entry until all entries have been processed or the function throws an exception (optional operation).
`int`	`size()`	Returns the number of key-value mappings in this map.

Methods declared in interface SequencedMap

firstEntry, lastEntry, pollFirstEntry, pollLastEntry, sequencedEntrySet, sequencedKeySet, sequencedValues

Modifier and Type	Method	Description
`default Map.Entry<K,V>`	`firstEntry()`	Returns the first key-value mapping in this map, or `null` if the map is empty.
`default Map.Entry<K,V>`	`lastEntry()`	Returns the last key-value mapping in this map, or `null` if the map is empty.
`default Map.Entry<K,V>`	`pollFirstEntry()`	Removes and returns the first key-value mapping in this map, or `null` if the map is empty (optional operation).
`default Map.Entry<K,V>`	`pollLastEntry()`	Removes and returns the last key-value mapping in this map, or `null` if the map is empty (optional operation).
`default SequencedSet<Map.Entry<K,V>>`	`sequencedEntrySet()`	Returns a `SequencedSet` view of this map's `entrySet`.
`default SequencedSet<K>`	`sequencedKeySet()`	Returns a `SequencedSet` view of this map's `keySet`.
`default SequencedCollection<V>`	`sequencedValues()`	Returns a `SequencedCollection` view of this map's `values` collection.

Method Details

comparator

Comparator<? super K> comparator()

Returns the comparator used to order the keys in this map, or null if this map uses the natural ordering of its keys.

Returns:: the comparator used to order the keys in this map, or null if this map uses the natural ordering of its keys

subMap

SortedMap<K,V> subMap(K fromKey, K toKey)

Returns a view of the portion of this map whose keys range from fromKey, inclusive, to toKey, exclusive. (If fromKey and toKey are equal, the returned map is empty.) The returned map is backed by this map, so changes in the returned map are reflected in this map, and vice-versa. The returned map supports all optional map operations that this map supports.

The returned map will throw an IllegalArgumentException on an attempt to insert a key outside its range.

Parameters:: fromKey - low endpoint (inclusive) of the keys in the returned map; toKey - high endpoint (exclusive) of the keys in the returned map
Returns:: a view of the portion of this map whose keys range from fromKey, inclusive, to toKey, exclusive
Throws:: ClassCastException - if fromKey and toKey cannot be compared to one another using this map's comparator (or, if the map has no comparator, using natural ordering). Implementations may, but are not required to, throw this exception if fromKey or toKey cannot be compared to keys currently in the map.; NullPointerException - if fromKey or toKey is null and this map does not permit null keys; IllegalArgumentException - if fromKey is greater than toKey; or if this map itself has a restricted range, and fromKey or toKey lies outside the bounds of the range

headMap

SortedMap<K,V> headMap(K toKey)

Returns a view of the portion of this map whose keys are strictly less than toKey. The returned map is backed by this map, so changes in the returned map are reflected in this map, and vice-versa. The returned map supports all optional map operations that this map supports.

The returned map will throw an IllegalArgumentException on an attempt to insert a key outside its range.

Parameters:: toKey - high endpoint (exclusive) of the keys in the returned map
Returns:: a view of the portion of this map whose keys are strictly less than toKey
Throws:: ClassCastException - if toKey is not compatible with this map's comparator (or, if the map has no comparator, if toKey does not implement Comparable). Implementations may, but are not required to, throw this exception if toKey cannot be compared to keys currently in the map.; NullPointerException - if toKey is null and this map does not permit null keys; IllegalArgumentException - if this map itself has a restricted range, and toKey lies outside the bounds of the range

tailMap

SortedMap<K,V> tailMap(K fromKey)

Returns a view of the portion of this map whose keys are greater than or equal to fromKey. The returned map is backed by this map, so changes in the returned map are reflected in this map, and vice-versa. The returned map supports all optional map operations that this map supports.

The returned map will throw an IllegalArgumentException on an attempt to insert a key outside its range.

Parameters:: fromKey - low endpoint (inclusive) of the keys in the returned map
Returns:: a view of the portion of this map whose keys are greater than or equal to fromKey
Throws:: ClassCastException - if fromKey is not compatible with this map's comparator (or, if the map has no comparator, if fromKey does not implement Comparable). Implementations may, but are not required to, throw this exception if fromKey cannot be compared to keys currently in the map.; NullPointerException - if fromKey is null and this map does not permit null keys; IllegalArgumentException - if this map itself has a restricted range, and fromKey lies outside the bounds of the range

firstKey

K firstKey()

Returns the first (lowest) key currently in this map.

Returns:: the first (lowest) key currently in this map
Throws:: NoSuchElementException - if this map is empty

lastKey

K lastKey()

Returns the last (highest) key currently in this map.

Returns:: the last (highest) key currently in this map
Throws:: NoSuchElementException - if this map is empty

keySet

Set<K> keySet()

Returns a Set view of the keys contained in this map. The set's iterator returns the keys in ascending order. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. If the map is modified while an iteration over the set is in progress (except through the iterator's own remove operation), the results of the iteration are undefined. The set supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Set.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations.

Specified by:: keySet in interface Map<K,V>
Returns:: a set view of the keys contained in this map, sorted in ascending order

values

Collection<V> values()

Returns a Collection view of the values contained in this map. The collection's iterator returns the values in ascending order of the corresponding keys. The collection is backed by the map, so changes to the map are reflected in the collection, and vice-versa. If the map is modified while an iteration over the collection is in progress (except through the iterator's own remove operation), the results of the iteration are undefined. The collection supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Collection.remove, removeAll, retainAll and clear operations. It does not support the add or addAll operations.

Specified by:: values in interface Map<K,V>
Returns:: a collection view of the values contained in this map, sorted in ascending key order

entrySet

Set<Map.Entry<K,V>> entrySet()

Returns a Set view of the mappings contained in this map. The set's iterator returns the entries in ascending key order. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. If the map is modified while an iteration over the set is in progress (except through the iterator's own remove operation, or through the setValue operation on a map entry returned by the iterator) the results of the iteration are undefined. The set supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Set.remove, removeAll, retainAll and clear operations. It does not support the add or addAll operations.

Specified by:: entrySet in interface Map<K,V>
Returns:: a set view of the mappings contained in this map, sorted in ascending key order

putFirst

default V putFirst(K k, V v)

Throws UnsupportedOperationException. The encounter order induced by this map's comparison method determines the position of mappings, so explicit positioning is not supported.

Specified by:: putFirst in interface SequencedMap<K,V>
Implementation Requirements:: The implementation in this interface always throws UnsupportedOperationException.
Parameters:: k - the key; v - the value
Returns:: the value previously associated with k, or null if none
Throws:: UnsupportedOperationException - always
Since:: 21

putLast

default V putLast(K k, V v)

Throws UnsupportedOperationException. The encounter order induced by this map's comparison method determines the position of mappings, so explicit positioning is not supported.

Specified by:: putLast in interface SequencedMap<K,V>
Implementation Requirements:: The implementation in this interface always throws UnsupportedOperationException.
Parameters:: k - the key; v - the value
Returns:: the value previously associated with k, or null if none
Throws:: UnsupportedOperationException - always
Since:: 21

reversed

default SortedMap<K,V> reversed()

Returns a reverse-ordered view of this map. The encounter order of mappings in the returned view is the inverse of the encounter order of mappings in this map. The reverse ordering affects all order-sensitive operations, including those on the view collections of the returned view. If the implementation permits modifications to this view, the modifications "write through" to the underlying map. Changes to the underlying map might or might not be visible in this reversed view, depending upon the implementation.

Specified by:: reversed in interface SequencedMap<K,V>
Implementation Requirements:: The implementation in this interface returns a reverse-ordered SortedMap view. The reversed() method of the view returns a reference to this SortedMap. Other operations on the view are implemented via calls to public methods on this SortedMap. The exact relationship between calls on the view and calls on this SortedMap is unspecified. However, order-sensitive operations generally behave as if they delegate to the appropriate method with the opposite orientation. For example, calling firstEntry on the view might result in a call to lastEntry on this SortedMap.
Returns:: a reverse-ordered view of this map, as a SortedMap
Since:: 21

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